1. Field of the Invention
The present invention relates to a structure of a motor including a housing formed by pressing.
2. Description of the Related Art
In recent years, due to reductions in size and price of a copier, a motor installed therein is also required to be further reduced in size and price.
A structure of a conventional motor will be described with reference to FIG. 19. FIG. 19 is a schematic cross sectional view of the conventional motor cut along an axial direction thereof.
Referring to FIG. 19, a motor 1 includes a shaft 2 disposed coaxially with a central axis J1, two bearing portions 3 axially spaced apart from each other to rotatably support the shaft 2, a housing 4 having a cylindrical portion 4a retaining the respective bearing portions 3 and a flange portion 4b extending radially outwards from the cylindrical portion 4a, a stator 5 fixed onto an outer peripheral surface of the cylindrical portion 4a of the housing 4, a rotor holder 6 having a cup shape and fixed to the shaft 2, a rotor magnet 7 fixed onto an inner peripheral surface of the rotor holder 6 to radially face the stator 5, and an attachment plate 8 attached to the housing 4. The housing 4 is shaped by die casting zinc alloy. The attachment plate 8 is caulked to be fixed onto a lower surface of the flange portion 4b of the housing 4. The attachment plate 8 is formed with a mounting portion 8a used for mounting the motor 1 to another device (not shown).
However, the housing 4 shaped by die casting zinc alloy requires expensive material and shaping costs, so that reduction in price of the motor cannot be realized as required. In addition, reduction in size of the motor is required particularly in an axial height from a lower surface of the mounting portion 8a to an upper surface of the rotor holder 6. Nonetheless, the attachment plate 8 is attached onto the lower surface of the flange portion 4b in the conventional motor 1, so that the position of the mounting portion 8a has been required to be axially lowered by a distance corresponding to a thickness of the attachment plate 8, resulting in difficulty in size reduction in the motor 1. Further, since the housing 4 and the attachment plate 8 are fixed to each other by caulking, a region 4c to be caulked projects axially downwards from the attachment plate 8. Therefore, the position of the mounting portion 8a has been required further to be axially lowered, resulting in further difficulty in size reduction in the motor 1.